Glycosphingolipids have for a long time been implicated in processes which involve recognition. Properties of glycolipids are believed to include: receptors for biologically active molecules, regulators of cell growth, and ability to act as recognition structures for cellular interactions during differentiation. The immune system provides an ideal model for such studies. It is endowed with great flexibility in which many subsets of cells cooperate in the induction of the immune response. These subsets are defined by serological markers which reflect differences in the surface chemistry of these subsets, which in turn reflects the differences in phy siological properties of these cells. Our long term objective is to obtrain a better understanding of the functional properties of glycosphingolipids in these recognition phenomena and to be able to identify and correct conditions in which defects in glycolipids are key elements in the mechanism of induction of disease. To this end we plan to continue a multi-faceted attack on this problem. First we will isolate and characterize as many lymphocy te glycolipids as possible, using newly dveloped, highly sensitive, methods which include high pressure liquid chromatography and mass spctrometry. Secondly, we will use mono-specific antibodies (conventional and monoclonal) in immuno-histochemical studies using the fluorescence activated cell sorter to define and isolate new subsets of lymphocytes in relationship to previously described functional subsets. For example, we will continue to examine the relationship between asialo Gm1 and its sialated derivatives with natural killer function in mice, using chemical, immunological and enzymological techniques. We will apply this same approach to the analysis of spontaneous leukemias and lymphomas in mice and humans in attempts to define the role of GSL in growth control, and we will apply our knowledge of the chemistry of unique lymphocyte glycolipid antigems to assess ther ability to interact with biologically active molecules in the lymphoreticular system, such s thymic hormones and lymphocy te growth factors.